The advent of optoelectronics and their potential to impact the communications industry has posed the problem to the manufacturing community to develop effective and cost efficient products to couple optoelectronic devices to end-user products such as computers and telecommunications equipment. The optoelectronic devices are for example optical transceivers which convert electrical signals to and from optical signals for communications frequencies in the gigahertz and megahertz frequency bands. As is well known to the skilled communications engineer, a crucial factor to transmission line/device interconnection is impedance matching. If the device and transmission line characteristic impedance are not properly matched, undesirable back-reflection results which significantly interferes with the effective transmission of data. To be specific, reflection due to impedance mismatch will result in interference of the signal carried to and from the device causing attenuation or distortion of the signal amplitude if the interference is destructive. This problem with interference with the reflected wave is dramatically pronounced in high frequency applications. For example, consider microprocessors which generate and receive digital pulses with extremely fast rise and fall times and operate in the 300 MHz to 1 GHz band. The skilled artisan will understand that the greater the frequency of the digital pulse, the greater the number of frequency components required to be mixed to effect the desired square pulse. This is particularly true the sharper the rise and fall times of the pulse. This follows by simple Fourier analysis. Clearly, in a such a system requiring a delicate mix of frequency components, any undesired components will result in an undesired waveform. As can be understood, the higher the frequency band in which devices operate, the more pronounced the ill-effects of reflection become. To be sure, as engineers attempt to increase data rates by using transmission frequencies in the microwave and millimeter wave spectral range, the ill-effects of reflection due to impedance mismatch are a true barrier to effective communication systems.
One technique of providing an easily manufactured, high frequency transmission line is disclosed in U.S. Pat. No. 4,680,557, to Compton and is incorporated herein by reference. Compton discloses the use of conventionally sized dielectric ribbon which provides high impedance and low distortion transmission line links between high frequency devices. Microstrip transmission line is fabricated by attaching thin metal strips to either side of the dielectric, with one side of parallel strips acting as signal lines and parallel strips acting as ground planes on the other side. Finally, the strips on either side are staggered so as to be offset relative to those on the opposite side of the ribbon. This can be seen in FIGS. 2 and 3 of the '557 reference. By utilizing this structure, the distance between the signal and ground lines is increased per given thickness of the dielectric, thereby decreasing the characteristic capacitance between the signal and ground lines to a negligible value. Furthermore, the effective width of the signal lines is increased as well. This enables high impedance transmission lines to be employed in parallel with some degree of control over the characteristic impedance of the waveguide. However, this flexibility is limited to the dimensional spacing of the strips as well as the intrinsic impedance of the dielectric ribbon. Furthermore, the reference does not disclose a structure capable of having mounted thereon an optoelectronic device. What is needed is a structure capable of having mounted or formed thereon an optoelectronic device as well as transmission lines for connecting to the device. The characteristic impedance of the transmission lines needs to be controllable to enable connection to various devices of differing characteristic impedances and the signal lines need to be of a dimension that enables easy electrical connection.